(a) Field of the Invention
The present invention relates to a compact zoom lens system and, more particularly, to a compact zoom lens system to be used with a camera with a lens shutter.
(b) Description of the Prior Art
A zoom lens system, which comprises a first lens group having negative refractive power and a second lens group having positive refractive power and which is arranged to be zoomed by varying the airspace between said lens groups, is known as a zoom lens system to be used chiefly with a single-lens reflex camera.
As the above-mentioned type of zoom lens system comprises a negative lens group and a positive lens group in the order from the object side, the principal point thereof comes to a position near the image surface and, therefore, the back focal length is long. This means that it is easy to ensure a space for accommodating a quick return mirror, and this is advantageous when uning said type of zoom lens system with a single-lens reflex camera. However, as the overall length of the lens system becomes long, said type of zoom lens system is not suitable for the use with a camera with a lens shutter and the like which requires compactness of a lens system.
The zoom lens system disclosed by Japanese published unexamined patent application No. 201213/82 is known as a zoom lens system which is arranged to be small in size to the degree that said lens system can be assembled in a camera with a lens shutter. Said known zoom lens system comprises a first lens group having positive refractive power and a second lens group having negative refractive power and is arranged to be zoomed by varying the airspace between said lens groups. Said known zoom lens system is arranged to make the overall length thereof short by adopting the so-called telephoto type lens composition. However, said known zoom lens system has disadvantages as described below. That is, as the diameter of the rearmost lens is large, the camera body as a whole tends to become large when the lens moving mechanism is included. Moreover, as the back focal length is too short, the quality of image tends to become unfavourable because of dirt on the rearmost lens surface.